Infusion pump

ABSTRACT

Infusion pumps according to the present invention maximize fluid throughput while minimizing vaporization of gas by employing specific flow path architecture, flow path dimensional ranges, and voltage and frequency ranges for activation of piezoelectric bodies.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/287,881 filed Dec. 18, 2009, entitled MEMS Pump for MedicalInfusion Pump; U.S. Provisional Application Ser. No. 61/287,903 filedDec. 18, 2009, entitled Pump Stay; U.S. Provisional Application Ser. No.61/287,912 filed Dec. 18, 2009, entitled Micro Infusion Pump SystemSoftware; U.S. Provisional Application Ser. No. 61/287,991 filed Dec.18, 2009, entitled Central Venous Pressure Monitoring Using MicroInfusion Pump, the contents of which are each incorporated in theirentirety herein.

FIELD OF THE INVENTION

The present invention relates to medical infusion pumps and relatedmethods and, more particularly, to infusion pumps employing thepiezoelectric effect for medical and healthcare related applications.

BACKGROUND OF THE INVENTION

Fluid pumps can be driven based on various design principles includingthe piezoelectric effect. The piezoelectric effect can be employed toindirectly cause fluid flow, for example a piezoelectric driven motor oractuator can be used to linearly displace a plunger to push fluid from areservoir or to rotate a rotor in a peristaltic-type pump. For example,U.S. Publication Nos. 2009/0124994 to Roe and 2009/0105650 to Wiegel etal., and U.S. Pat. Nos. 7,592,740 to Roe, and 6,102,678 to Perclat teachthe application of such technologies to infusion pumps used in themedical and health care industries.

Alternatively, the piezoelectric effect can be employed to cause fluidflow through the direct manipulation of a fluid chamber or flow path,for example through vibration of an internal surface of a fluid chamber.Such microelectromechanical system, or MEMS, micropumps can befabricated using known integrated circuit fabrication methods andtechnologies. For example, using integrated circuit manufacturingfabrication techniques, small channels can be formed on the surface ofsilicon wafers. By attaching a thin piece of material, such as glass, onthe surface of the processed silicon wafer, flow paths and fluidchambers can be formed from the channels and chambers. A layer ofpiezoelectric material, or a piezoelectric body such as quartz, is thenattached to the glass on the side opposite the silicon wafer. When avoltage is applied to the piezoelectric body, a reverse piezoelectriceffect, or vibration, is generated by the piezoelectric body andtransmitted through the glass to the fluid in the chambers. In turn, aresonance is produced in the fluid in the chambers of the silicon wafer.Through the inclusions of valves and other design features in the fluidflow paths, a net directional flow of fluid through the chambers formedby the silicon wafer and the glass covering can be achieved.

MEMS micropumps have become an established technology in the inkjetprinter industry. Technological developments relating to increaseddefinition and ink throughput for piezoelectric micropumps, or MEMSmicropumps, for inkjet printers have achieved more precise printing withsmaller ink throughputs. For example, it has become possible to controlthe ink throughput of inkjet printers employing MEMS micropumps at thepicoliter level. Furthermore, in order to address the problemsassociated with uneven printing in inkjet printers due to thevaporization of gas dissolved in the ink, considerable development hasalso been directed to providing inkjet printers with structures fordegassing the ink.

MEMS micropumps employing the piezoelectric effect have also beencontemplated for use in small and large-volume infusion pumps, i.e. pumpsystems that are typically employed to infuse fluids, medications, andnutrients into a patient's circulatory system. For example, with respectto small-volume infusion systems, U.S. Pat. Nos. 3,963,380 to Thomas,Jr. et al.; 4,596,575 to Rosenberg; 4,938,742 to Smits; 4,944,659 toLabbe et al.; 5,984,894 to Poulsen et al.; and 7,601,148 to Keller alldescribe various micropumps intended for implantation into a patient inorder to administer small amounts of pharmaceuticals, such as insulin.Similarly, U.S. Publication No. 2007/0270748 to Dacquay et al. describesa piezoelectric micropump integrated into the tip of a syringe for verylow volume delivery of ophthalmic pharmaceuticals to a patient's eye.

In contrast to inkjet printers and small-volume infusion micropumps,large-volume infusion pumps must be operable to provide significantlyincreased fluid throughput. However, as fluid throughput, or fluid flowrates are increased, the potential for the vaporization of dissolved gascorrespondingly increases. Those skilled in the art will recognize thatthe vaporization of dissolved gas within the fluid flow paths ofinfusion pump systems presents a significant health hazard to patientsreceiving infusions. While the problems associated with thevaporizations of dissolved gas in inkjet printer micropumps, systems inwhich fluid throughputs are relatively low, has largely been addressedthrough the development of degassing technologies, satisfactorysolutions have not been presented for high-throughput micropumps, suchas infusion pumps, used in the health and medical industry. U.S.Publication No. 2006/0264829 to Donaldson and U.S. Pat. No. 5,205,819 toRoss et al. described large-volume infusion systems employingpiezoelectric micropumps; however, neither of these systems providessolutions directed to overcoming the problems associated withvaporization of dissolved gas at high fluid throughputs.

What is needed in the field is a highly accurate infusion pump systemthat provides high fluid throughput while reducing or eliminating therisk of the vaporization of dissolved gasses within the fluid flow path.

OBJECTS AND SUMMARY OF THE INVENTION

The infusion pumps according to the present invention provide highlyaccurate infusion pump systems that provides high fluid throughput whilereducing or eliminating the risk of vaporization of dissolved gasseswithin the fluid flow path. Infusion pumps according to the presentinvention achieve these advances by employing specific flow patharchitecture, flow path dimensional ranges, and voltage and frequenciesranges that, relative to one another, serve to provide an infusion pumpthat maximize fluid throughput while minimizing vaporization of gas.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a perspective view of an infusion pump according to oneembodiment of the present invention.

FIG. 2 a is a perspective view of a micropump according to oneembodiment of the present invention.

FIG. 2 b is a cross-sectional view taken along line b of FIG. 2 a of amicropump according to one embodiment of the present invention.

FIG. 2 c is a plan view of a pump base of a micropump according to oneembodiment of the present invention.

FIG. 2 d is an expanded plan view of a portion 35 of FIG. 2 c of a pumpbase of a micropump according to one embodiment of the presentinvention.

FIG. 3 is a plan view of flow channels and cambers of a micropumpaccording to one embodiment of the present invention.

FIG. 4 is a graphical representation of a power provided to a micropumpaccording to one embodiment of the present invention.

FIGS. 5 a and 5 b are cross-sectional views of a micropump according toone embodiment of the present invention.

FIG. 6 is a plan view of a micropump according to one embodiment of thepresent invention.

FIG. 7 is a plan view of a micropump according to one embodiment of thepresent invention.

FIG. 8 a is a side elevation view of a micropump according to oneembodiment of the present invention.

FIG. 8 b is a plan view of a micropump according to one embodiment ofthe present invention.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

Infusion pumps according to the present invention provides unique flowpath and fluid chamber structure in order to provide highly accuratefluid flow and relatively high fluid throughput while reducing oreliminating the risk of vaporization of dissolved gas within the fluidflow path.

As shown in FIG. 1, an infusion pump 10 according to one embodiment ofthe present invention comprises a pump body 20 a having an inlet port22, an outlet port 24, and a communication port 26. Situated within body20 a is a MEMS micropump. As shown in FIG. 2 a and the cross-sectionalview of FIG. 2 b taken along line b of FIG. 2 a, the MEMS micropump, ormicropump, 30 comprises a piezoelectric body 32 having a thicknessindicated as d3 attached to one side of a vibration layer 36. Thevibration layer 36 may be fabricated from glass, quarts, alloy or apolymer-based material. An opposite side of the piezoelectric body 32 isin electrical contact with an electrode 34, and an opposite side of thevibration layer 36 is affixed to a pump base 38. As shown in FIG. 2 band the plan views of the pump base 38 shown in FIGS. 2 c and 2 d,formed within the pump base 38 are flow channels and fluid chambers.More particularly, the pump base 38 comprises inlet channel 40, outletchannel 42, and chamber 44. The chamber 44 has a length I1 and a widthI2. A distance from a bottom 46 of the chamber 44 to a top of thechamber 44 formed by the vibration layer 36 is indicated as a depth d.It will be understood that the depth d is determined in the approximatecenter or middle of the chamber 44. An inclination or angle of thebottom 46 of the chamber 44 relative to the bottom 48 of the pump base38 is indicated as an angle R1. While only one angle R1 has beendescribed, it will be understood that the bottom 46 of the chamber 44may be angled relative to the bottom 48 of the pump base 38 in more thanone plane of reference. As shown in FIG. 2 b, as a result of theinclination or angle of the bottom 46 of the chamber 44, the chamber 44has a cross-sectional area that is greatest approximate the outletchannel 42. The inlet channel 40 and the outlet channel 42 are eachformed on opposite sidewalls of the chamber 44, are each continuouslyopen to fluid flow, and each comprises a differently configured channelconstriction or cross-sectional shape.

The piezoelectric body 32 may comprise various known materials havingpiezoelectric properties, including naturally occurring crystals such asquartz, man-made crystals and man-made ceramics and polymers.

The pump base 38 may be fabricated from silicon; such as the siliconwafers employed in known integrated circuit fabrication techniques, ormay be fabricated from other sufficiently rigid materials such asvarious metals, alloys, and polymers. It will be understood that, basedupon the specific material(s) from which the pump base 38 is fabricatedas well as, the specific technique employed for creating the channelsand chambers within the pump base 38, the surfaces of the channels andchambers may be smooth and/or stepped. For example, if the pump base 38is fabricated using known integrated circuit fabrication techniques, theinclination or angle of the bottom 46 of the chamber 44 may be formed byremoving silicon in defined steps according to the various masksemployed. Accordingly, the sloped surface of the bottom 46 of thechamber 44 would be stepped rather than smooth. Conversely, if the pumpbase 38 is fabricated from a metal or alloy, the inclination or angle ofthe bottom 46 of the chamber 44 may be formed such that the surface ofthe bottom 46 of the chamber 44 is smooth.

Formed within the inlet channel 40 is a constriction A, and formedwithin the outlet channel 42 is a constriction B. It will be noted thatthe constrictions A and B may narrow in a horizontal, vertical, orhorizontal and vertical directions. A length of the inlet channel 40from the constriction A to the side 50 of the chamber is indicated asI3. A width of the inlet channel 40 upstream of the constriction A isindicated as L1, and a width of the constriction A is indicated as L2.

As shown best in FIG. 2 d, between the constriction A and a chamberinlet 52, the inlet channel 40 has a funnel-like or triangular form. Anangle defined by this funnel-like form of inlet channel 40 between theconstriction A and a chamber inlet 52 is indicated as R2. The width ofthe chamber inlet 52 is indicated as L3. In operation, the piezoelectricbody 32 vibrates in the directions indicated by arrow 33 as a result ofa voltage V applied to the piezoelectric body 32 through the electrode34 at a frequency n. The vibration of the piezoelectric body 32 istransferred to a fluid within the chamber 44 through the vibration layer36 thereby producing a resonance in the fluid within the chamber 44. Apumping, or a net directional flow, of the fluid within the chamber 44occurs in accordance with the resistances created by the constrictions Aand B formed in the inlet channel 40 and the outlet channel 42respectively.

It will be understood that the resonance created within the chamber 44,and thereby the flow of fluid through the micropump 30, is influenced bygeometry of the chamber 44 and inlet and outlet channels 40 and 42. Alsoinfluencing the resonance is the frequency, the voltage, and the shapeof the wave that contribute to the piezoelectric effect of thepiezoelectric body. Therefore, micropumps 30 according to the presentinvention are optimized with respect to the following parameters: (1)the length I1 of the chamber 44; (2) the width I2 of the chamber 44; (3)the depth d of the chamber 44; (4) the angle R1 defined by the bottom 46of the chamber 44 relative to the bottom 48 of the pump base 38; (5) thenumber of micropumps or micropump chambers 44 employed in the system;(6) the configuration of the constriction A relevant to the inletchannel 40 up stream of the constriction A; (7) the configuration of theconstriction A relevant to the chamber inlet 52 downstream of theconstriction A; vibration layer 36 (8) the thickness d3 of thepiezoelectric body 32 and the number of piezoelectric bodies 32employed; and (9) the voltage V applied to the piezoelectric body 32 atthe frequency n.

Turning first to the relevant parameters regarding the chamber 44 of themicropump 30, in order to achieve a high fluid throughput, micropumps 30according to the present invention employ a relatively large-volumechamber 44. The shape of the chamber 44, that is to say, therelationship of the length to width to depth of the chamber 44 is animportant consideration in order to optimize the resonance phenomenagenerated in the fluid within the chamber 44. For example, the depth dof the chamber 44 influences the magnitude of the resonance which, inturn, increases fluid throughput. However, at extreme magnitudes, theresonance of the liquid in the chamber 44 will undesirably occur only atthe upper layer of the fluid and fluid throughput will decrease.

Relative to the other optimized parameters herein provided formicropumps 30 according to the present invention, the distance d from abottom 46 of the chamber 44 to a top of the chamber 44 formed by thevibration layer 36 is preferably 50 to 300 micrometers and morepreferably 100 to 200 micrometers. The length I1 of the chamber 44 ispreferably within the range of 1 to 30 millimeters, and the width I2 ofthe chamber 44 is preferably within the range of 1 to 5 millimeters.Within the preferred range on depths d, a preferred range of length towidth ratios is 1:1 to 6:1 and more preferably 4:1. For example, anoptimized chamber 44 may have a length I1 of 4 millimeters and a widthI2 of 1 millimeters and a depth of 200 micrometers.

Also related to the shape of the chamber 44 is the angle R1 defined bythe bottom 46 of the chamber 44 relative to the bottom 48 of the pumpbase 38. The angle R1 serves to bias the resonance towards the outletchannel 42 side of the chamber 44, i.e. towards the right side of thechamber 44 as shown in FIGS. 2 b and 2 c. While a greater angle R1increases the fluid throughput, at overly steep angles, the resonance atthe downstream side of the chamber 44 and thereby fluid throughput willtend to decrease. Relative to the other optimized parameters hereinprovided for micropumps 30 according to the present invention, the angleR1 defined by the bottom 46 of the chamber 44 relative to the bottom 48of the pump base 38 is preferably in the range of zero to 50 degrees andmore preferably between 0.01 to 10 degrees.

In situations in which one micropump 30 does not provide the desiredthroughput, a micropump 30 having increased throughput can be formed bycombining a number N of chambers 44 in parallel or in series. In suchmulti-chamber 44 pumps, identical chambers 44 may be combined, or asshown in FIG. 3, chambers 44 having differing sizes and throughputs maybe combined. Pumps having a plurality of chambers 44 of different sizesand or dimensions operable of providing different fluid throughputs,allow for a more precise throughput control and a broader throughputrange. For example, in cases such as those wherein the throughput is tobe varied, advantages such as better precision and a wider range ofthroughputs can be achieved by combining a 100 milliliter per hourchamber 44 a and a 10 milliliter per hour chamber 44 b. In medicalsettings, this is advantageous in so much as it is not necessary tochange pumps, even when changing from 100 milliliter per hour of a drugto 10 milliliter per hour of a drug.

Turning now to the relevant parameters regarding the constriction A andthe inlet channel 40 upstream of the constriction A. It is noted that asmaller width L2 of the constriction A is associated with increasedthroughput, however, a smaller width L2 is also associated withincreased negative pressure downstream from the constriction A. This, inturn, results in an increased undesirable vaporization of dissolved gas.Relative to the other optimized parameters herein provided for pumpsaccording to the present invention, the width L2 of the constriction Ais preferably in 30 to 200 micrometers and more preferably 40 to 80micrometers, for example 50 micrometers. The width L1 of the inletchannel 40 upstream of the constriction A is preferably 50 to 300micrometers and more preferably 80 to 100 micrometers, for example 80micrometers. The range of the ratio L2:L1 is preferably 0.13 to 0.67.

Turning now to the relevant parameters regarding the constriction A andthe inlet channel 40 downstream of the constriction A. The constrictionwidth angle R2 is defined by this funnel-like, or triangular, form ofinlet channel 40 between the constriction A and the chamber inlet 52.Alternatively stated, the constriction width angle R2 refers to theangle formed at the apex of a triangle formed by the length I3 and thewidth L3. While increasing the constriction width angle R2 achieves agreater fluid throughput, increasing the constriction width angle R2also increases the negative pressure upstream of the constriction A. Theangle R2 is determined by the formula:

${R\; 2} = {2({tangent})\left( \frac{\left( {{L\; 3} - {L\; 2}} \right)0.5}{I\; 3} \right)}$

Alternatively stated the angle R2 is equal to two times the tangent ofL3 minus L2 times 0.5 divided by I3. Relative to the other optimizedparameters herein provided for pumps according to the present invention,width L2 of the constriction A is preferably in 30 to 200 micrometersand more preferably 50 micrometers; width L3 of the chamber inlet 52 ispreferably 50 to 300 micrometers and more preferably 80 micrometers; andthe length I3 of the inlet channel 40 from the constriction A to thechamber outlet 52 is preferably 1 to 15 millimeters and more preferably10 millimeters. The constriction width angle R2 is preferably 0.00001 to10 degrees and more preferably 0.0005 degrees.

Turning now to the relevant parameters of the piezoelectric body 32,employing a thicker piezoelectric body 32 results in increased vibrationwhich causes greater resonance to be produced thereby increasing fluidthroughput. However, increased resonance may also result in increasednegative pressure at the constriction A, thereby causing vaporization ofdissolved gas. In order to increase the pumping rate, two or threepiezoelectric bodies having thicknesses of 0.1 millimeter to 1millimeter can be stacked.

Finally, with respect to the voltage V applied to the piezoelectric body32 at the frequency n, increases in frequency and/or voltage withinitially increase fluid throughput. Relative to the other optimizedparameters herein provided for micropumps 30 according to the presentinvention, the frequency n is preferably in the range of 50 to 4500hertz. With respect to voltage, the higher the voltage, the greater theamplitude at which the piezoelectric body will vibrate, which will causean increase the resonance phenomena produced within the chamber, andincrease fluid flow. However, strong resonance phenomena will alsoproduce a greater negative pressure at the constriction A, which willresult in vaporization of dissolved gasses. Accordingly, relative to theother optimized parameters herein provided for pumps according to thepresent invention, the voltage V is preferably in the range of 20 to 100volts.

Furthermore, the manner in which the voltage is applied also influencesthe throughput of micropumps according to the present invention. Forexample, the negative pressure in the area of the constriction A andthus the vaporization of dissolved gas is controlled by controlling therate of rise of the voltage V. FIG. 4 shows the manner in which thevoltage is preferably applied. In the graph provided in FIG. 4, thehorizontal axis 60 represents the passage of time and the vertical axis58 represents increasing voltage. Line 56 is provided as a referenceline from which angle R3 is determined. Relative to the other optimizedparameters herein provided for pumps according to the present invention,in order to reduce or prevent vaporization of dissolved gas, angle R3 ispreferably in the range of 3 to 45 degrees.

The infusion pumps 10 according to the present invention are operable toprovide fluid flow rates of up to approximately 280 milliliters per hourand greater. It will be understood, however, that the flow rate achievedby the infusion pump 10 is dependent upon the back pressure imparted bythe patient's circulatory system. Accordingly, as the back pressureimparted on the infusion pump 10 increases, the control factors providedto the micropump 30 must be changed in order achieve the desired flowrate while overcoming such back pressure. For example, while maintainingall other design parameters and control factors constant, at backpressure of zero kilopascal, the infusion pump 10 according to thepresent invention may achieve a flow rate of approximately 780microliters per minute at a frequency of 50 hertz, or Hz; 1,610microliters per minute at a frequency of 100 Hz; and 1,930 microlitersper minute at a frequency of 150 Hz. At back pressure of 60 kilopascal,the infusion pump 10 according to the present invention may achieve aflow rate of approximately 230 microliters per minute at a frequency of50 Hz; 440 microliters per minute at a frequency of 100 Hz; and 630microliters per minute at a frequency of 150 Hz.

In yet another embodiment of the present invention, as shown in FIGS. 5a and 5 b, a micropump 330 comprises the piezoelectric body 32 attachedto one side of the vibration layer 36. An opposite side of the vibrationlayer 36 is affixed to the pump base 38. The pump base 38 comprises theinlet channel 40, the outlet channel 42, and the chamber 44. In contrastto the micropump 30 described above, the micropump 330 further comprisesinlet valve 60 and outlet valve 62. The inlet valve 60 and the outletvalve 62 are operable to transpose as shown in FIGS. 5 a and 5 b.

In operation, when the piezoelectric body 32 is manipulated in thedirection of arrow 64, chamber 44 becomes negatively pressurized andinlet valve 60 opens allowing fluid flow into the chamber 44.Conversely, outlet valve 62 is pulled closed thereby discouraging anybackflow of fluid in to the chamber 44. When the piezoelectric body 32is manipulated in the direction of arrow 66, chamber 44 becomespositively pressurized. Inlet valve 60 is pushed closed therebypreventing flow out through the inlet channel 40. Conversely, outletvalve 62 is opened to allow fluid flow through the outlet channel 42.

It will be understood that features, such as the valves 60 and 62,described above with respect to micropump 330 may be combined with anyof the design features described with respect to micropumps 30 and viceversa in order to achieve micropumps according to the present invention.

As shown in FIG. 6, the infusion pump 10 according to the presentinvention further comprises a first circuit 70, a second circuit 72 andflow meter 74. The first circuit provides power to the electrode 34,shown in FIG. 2 a, and the second circuit 72 provides power to the flowmeter 74 and AC/DC conversion of the data from the sensors associatedwith the flow meter 74. The first and second circuits 72 and 74 areaccordingly in electrical communication with a power source such as awall mounted plug, a battery, or a combination thereof. The obviousadvantage of an infusion pump 10 employing a battery is thecorresponding mobility of the infusion pump 10 while maintaininguninterrupted flow of infusion fluids.

The flow meter 74 associated with the infusion pump 10 may comprise avariety of know flow meters. The flow meter 74 may comprise a variety ofknown flow meters. For example, the flow meter 74 may be configured todetermine fluid flow rates by employing a heater that heats the fluidbeing monitored and senses the flow of the heated fluid downstream ofthe heater. Such flow meters are available from Sensirion AG ofSwitzerland and Siargo Incorporated of the United States of America andare described in greater detail in at least U.S. Pat. No. 6,813,944 toMayer et al. and U.S. Publication No. 2009/0164163, which are hereinincorporated by reference. Alternatively, the flow meter 74 may beconfigured to employ two pressure sensors positioned on each side of aconstriction within the fluid flow path. Fluid flow rates are determinedby the relative difference between the pressure sensors and changesthereof.

It is noted that while infusion pump 10 has been depicted as a singleunit or component in FIGS. 1 and 6, certain elements of the infusionpump 10 may be compartmentalized within different components or bodies.For example, FIG. 7 shows an infusion pump 10 in which first and secondcircuits 70 and 72, respectively, housed in body 20 b separate from themicropump 30, 330 and the flow meter 74 which are contained in body 20a. Such as system is advantageous for several reasons. For example, itmay be preferable to fabricate body 20 a comprising the micropump 30,330 and the flow meter to be disposable. Accordingly, risk ofcontamination and the costs associated with cleaning and preparing themicropump 30, 330 and flow meter 74 for use with different patients canbe decreased. However, in order that the cost of production of theinfusion pump may be minimized, it may be desirable to make as few aspossible of the components of the infusion pump 10 disposable.Accordingly, body 20 b in which the circuits 70 and 72 are contained maybe considered non-disposable, or reusable.

The infusion pump 10 of the present invention comprising multiplebodies, such as bodies 20 a and 20 b, may employ structures to establishelectrical communication between one another. For example, as shown inFIG. 1, body 20 a may comprise a communication port 26 through which thefirst and second circuits 70 and 72 may be placed in electricalcommunication with the electrode 34 of the micropump 30 and the flowmeter 74, respectively. The communication port 26 may be fabricated froma variety of electrical connectors/terminals and wire types known in theart.

Alternatively, as shown in FIG. 8 a, the body 20 a and the body 20 b maybe formed such that the bodies can be physically attached to oneanother. For example, body 20 a comprises recesses 76 formedsubstantially around a perimeter of the body 20 a. Body 20 b, in turn,comprises binders 78 positioned also substantially around a perimeter ofthe body 20 b. The binders 78 are deflectable and shaped to fit into therecesses 76 formed in the body 20 a. When the disposable body 20 a is tobe mated with the non-disposable body 20 b, the two bodies are pressedagainst one another thereby forcing the binders 78 to deflect outwardaround the base 84 of the body 20 a until the binders 78 engage therecesses 76 of the body 20 a. Once the binders 78 of the body 20 bengage the recesses 76 of the body 20 a, the two bodies are pulledtowards one another and maintained in friction fit.

Electrical communication is established between bodies 20 a and 20 bthrough complementary electrodes 82 formed on the surface 86 of the body20 a and the surface 88 of the body 20 b.

In certain embodiments of the present invention, is may be desirable toseal the electrodes 82 within a fluid tight environment. Accordingly,seal 80 may be embedded in the surface 86 of the body 20 a and/or in thesurface 88 of the body 20 b. Upon mating of the two bodies 20 a and 20b, the seal 80 is engaged and a fluid tight environment is establishedaround the electrodes 82. The seal 80 may comprise a soft, yieldingmaterial such as Teflon, silicone, or other polymeric material. In orderto prevent the seal 80 from moving, the seal may be embedded at leasthalfway into the surface in which it is attached.

It will be noted that because the piezoelectric body 32 vibrates duringoperation, the construction and mating of the bodies 20 a and 20 b mustbe sufficient to maintain the electrical communication between thebodies. For this, it is necessary that any wires with which thepiezoelectric body 32 is connected to the electrodes of the body 20 a bemade from a material that is flexible, and which bonds strongly with thepiezoelectric body.

In certain embodiments of the present invention, a user interface orindicator, not shown, is provided on the body 20 b. The user interfacemay provide information such as the name and specifications of the fluidor pharmaceutical(s) being infused by the pump. The user interface mayalso be color-coded, so that the type of drug can be easily recognized.If multiple drugs are to be injected, in a system in which multipleinfusion pumps 10 are employed, the user interface may provide pumpidentifiers that allow the user to easily identify a specific pump. Theuser interface may also provide warning lights that alert a user ofparticular operation parameters or operating conditions that have beenencountered.

In yet another embodiment of the present invention, infusion pump 10further comprises a control terminal, not shown, that is in electricalcommunication with the first and second circuits 70 and 72. The controlterminal serves to provide control factors to the micropump 30.Micropump 30 control factors include, for example, the voltage V appliedto the piezoelectric body 32 at the frequency n and the manner or rateat which the voltage V is increased and decreased during operation. Thecontrol terminal is in wireless or wired communication with the firstand second circuits 70 and 72. In a one embodiment, a nurse or othercaregiver may employ one control terminal to independently establishelectrical communication with and thereby control a single infusion pump10. Once the control factors have been provided to the infusion pump 10,the same control terminal may be carried or otherwise transported to adifferent infusion pump 10 in order to provide the control factors forthe second infusion pump 10. Stated alternatively, it is contemplatedthat, for example, in a hospital setting, a plurality of differentinfusion pumps 10 can be controlled by a single control terminal. Insuch an embodiment, the control terminal may also serve to receive fluidflow rate data from the flow meter 74 associated with the infusion pump10.

In another embodiment, the control terminal comprises a centralizedpatient fluid management system that is associated with a single patientduring the course of the patient's treatment, i.e. the control terminalis not shared between multiple patients. In such an embodiment, thecontrol terminal is operable to provide control factors to a pluralityof infusion pumps 10, receive flow rate data from the flow meter 74,receive patient biological data from various patient sensors associatedwith the control terminal, and to provide various patient information tothe caregiver based upon such patient data received. Such a controlterminal is described in greater detail in the Assignee's U.S. patentapplication Ser. No. 12/972,374, entitled Patient Fluid ManagementSystem, filed Dec. 17, 2010.

Of particular significance, is the fact that the micropump 30 of theinfusion pump 10 does not exchange data with the control terminal, i.e.the electrical communication between the micropump 30 and the controlterminal is one-way, from the control terminal to the micropump 30. Themicropump 30 is a slave to the control terminal. This configuration isadvantageous because it provides for a simplified and more economicalinfusion pump 10. For example, by making the micropump 30 a slave of thecontrol terminal, the circuitry within the micropump 30 is simplifiedand thereby more economical to manufacture. In view of the abovedescribed embodiments in which the micropump 30 is disposable, ahospital or clinic may more economically obtain the disposable portionsof the infusion pump 10 and only have to acquire and maintain a limitednumber of the more complex and more costly control terminals.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. An infusion pump comprising: an inlet channelformed on a first side of a fluid chamber and an outlet channel formedon a second side of the fluid chamber opposite the first side, the inletchannel being continuously open to fluid flow, a portion of the inletchannel having a reduced cross-sectional area; the fluid chamber havinga cross-sectional area that is greatest nearest the outlet channel; anda piezoelectric body having a first side attached to an exterior surfaceof the fluid chamber and a second side attached to an electrode.
 2. Theinfusion pump of claim 1 wherein the fluid chamber has a depth thatvaries at an angle greater than zero degrees and less than or equal toan angle of 10 degrees relative to an exterior surface of the chamber.3. The infusion pump of claim 1 wherein the fluid chamber furthercomprises a length to width ratio of
 4. 4. The infusion pump of claim 1wherein a width of the inlet channel varies along at least two differentlengths of the inlet channel.
 5. The infusion pump of claim 1 whereinthe fluid chamber is formed at least in part of a metal.
 6. The infusionpump of claim 1 wherein an angle formed by opposite walls of the inletchannel is approximately 0.0005 degrees.
 7. The infusion pump of claim 1further comprising a first body containing at least the piezoelectricbody and a second body containing at least a power supply circuit.
 8. Aninfusion pump comprising: a first body comprising a fluid chamberinterposed between a fluid inlet channel and a fluid outlet channel, thefluid chamber having a cross-sectional area that is greatest nearest thefluid outlet channel; and a piezoelectric body having a first sideattached to an exterior surface of the fluid chamber and a second sideattached to an electrode.
 9. The infusion pump of claim 8 wherein theinlet channel is continuously open to fluid flow.
 10. The infusion pumpof claim 8 wherein a portion of the inlet channel has a reducedcross-sectional area.
 11. The infusion pump of claim 8 wherein the fluidchamber has a depth that varies at an angle greater than zero degreesand less than or equal to an angle of 10 degrees relative to an exteriorsurface of the chamber.
 12. The infusion pump of claim 8 wherein thefluid chamber further comprises a length to width ratio of
 4. 13. Theinfusion pump of claim 8 wherein a width of the inlet channel variesalong at least two different lengths of the inlet channel.
 14. Theinfusion pump of claim 8 wherein the fluid chamber is formed at least inpart of a metal.
 15. The infusion pump of claim 8 wherein an angleformed by opposite walls of the inlet channel is approximately 0.0005degrees.
 16. The infusion pump of claim 8 further comprising a firstbody containing at least the piezoelectric body and a second bodycontaining at least a power supply circuit.